Sensor devices that utilize the electrical field enhancing effect due to localized plasmon on the surfaces of metals and electrical field enhancing devices of Raman spectroscopic devices are known. Raman spectroscopy is a technique that obtains the spectrum of Raman scattered light (Raman spectrum) by spectrally analyzing scattered light obtained by irradiating a substance with a single wavelength light beam, and is utilized to identify substances.
There is a Raman spectroscopy technique called SERS (Surface Enhanced Raman Scattering) that utilizes an optical electrical field enhanced by localized plasmon resonance in order to amplify weak Raman scattered light (refer to S. Ghadarghadr et al., “Plasmonic array nanoantennas on layered substrates: modeling and radiation characteristics”, OPTICS EXPRESS, Vol. 17, No. 21, pp. 18556-18570, 2009). SERS utilizes the principle that when light is irradiated onto a metal body, particularly a metal body having nano order protrusions and recesses on the surface thereof, while the metal body is in contact with a substance, optical electrical field enhancement occurs due to localized plasmon resonance, and the intensity of Raman scattered light of a sample in contact with the surface of the metal body is amplified. Surface enhanced Raman scattering can be executed by employing a substrate having a metal structure of protrusions and recesses on the surface thereof as a carrier (substrate) that holds test subjects.
Si substrates, on the surface of which protrusions and recesses are provided, having metal films formed on the surface having the protrusions and recesses, are mainly employed as substrates having metal structures of protrusions and recesses on the surfaces thereof (refer to PCT Japanese Publication No. 2006-514286. Japanese Patent No. 4347801, and Japanese Unexamined Patent Publication No. 2006-145230).
In addition, an Al substrate, the surface of which is anodized such that a portion thereof becomes a metal oxide layer (Al2O3) and a plurality of fine pores which are formed naturally within the metal oxide layer during the anodizing process are filled with metal, has also been proposed (refer to U.S. Pat. No. 7,288,419).